Others have applied a label or a protective covering of a plastic sheet material to a bottle, jar or other container by first forming a sleeve of the sheet material, and then sliding the sleeve over the container and heat shrinking it tightly around the container to conform to the contours thereof. This method is described and illustrated in Amberg et al, U.S. Pat. No. 3,767,496 for a "Method Of Making A Plastic-Covered Glass Container", and in related U.S. patents. However, in applying a label or a wrapper to containers in accordance with this method, it is necessary to perform the extra of first forming the cylindrical sleeve by wrapping it onto a separate mandrel or former, before it is even applied to the container.
The present inventor previously developed a method of forming the sleeve directly on the container itself, thereby omitting the step of sliding the sleeve onto the container before heat shrinking it tightly in place. Then, after the container is emptied, and is to be salvaged for recycling, the label is easily removed because the glue, which is applied to attach the label to the container, is weakened during heat shrinking. Specifically, the label is applied to the container by adhering it with glue on the leading edge, wrapping the label around the container and applying a solvent of the plastic label to the trailing edge so that when the trailing edge overlaps the leading edge, the solvent acts on both trailing and leading edges to bond them together. This bond is enhanced during heat shrinking. This method works very satisfactorily in practice, provided that the container has a cylindrical surface that is wide enough to hold the label in place until it is wrapped around the container and the overlapped edges are bonded together. However, there are many containers today that are of contoured configuration, with only a portion thereof that is of the maximum large cylindrical configuration. Where the cross-section is reduced, conventional rollers and brushes cannot press the label against the container to adhere it across its full height.
In an invention which is related to the present invention being described and claimed in my co-pending U.S. patent application Ser. No. 07/363,055 filed Jun. 6, 1989 for "Method of Applying a Thermoplastic Strip to a Container", now U.S. Pat. No. 4,911,772 dated, a heat shrinkable strip is applied to the large end of a container after pressing a cylindrical vacuum mandrel against that end of the container. The thermoplastic strip is wrapped around both the container and the mandrel to extend around reduced diameter portions of the container. After the strip is heat-shrunk around that end of the container to interlock therewith, the mandrel is withdrawn and the remainder of the strip is then heat-shrunk over the top of the container to form a tamper-evident seal.